JP7594932B2 - Fuel cell separator member and method for manufacturing fuel cell separator member - Google Patents

Description

The present invention relates to a fuel cell separator member, a method for manufacturing a fuel cell separator member, and a fuel cell separator.

One method for increasing the power generation efficiency of a fuel cell is to improve the electrical conductivity of the fuel cell separator. For example, Patent Document 1 discloses a fuel cell separator that uses a thermoplastic resin sheet containing conductive powder particles. Patent Document 2 discloses a fuel cell separator that uses an organic sheet coated with a mixture of carbonaceous powder and resin.

The conductivity of this fuel cell separator can be evaluated using the through resistance (resistivity in the thickness direction) and the volume resistivity (resistivity per unit volume). The lower the through resistance and volume resistivity, the better.

JP 2006-332035 A JP 2006-172776 A

However, although these fuel cell separators are conductive, they still have the problem of having high through-hole resistivity (resistivity in the thickness direction) and volume resistivity (resistivity per unit volume).

The present invention has been made in consideration of the above circumstances, and aims to provide a fuel cell separator having low through-hole resistivity and volume resistivity, a fuel cell separator member constituting the fuel cell separator, and a method for manufacturing the fuel cell separator member.

To achieve the above object, [1] the fuel cell separator member of the present invention comprises a prepreg layer in which a substrate is impregnated with a thermosetting resin composition containing carbon-based powder, and resin layers made of a thermosetting resin composition containing graphite laminated on both sides of the prepreg layer, and the volume resistivity of the resin layer is lower than that of the prepreg layer.

[2] The substrate may also be made of a woven fabric.

[3] The graphite may also have a flake shape.

[4] The resin layer may also include voids.

[5] The thermosetting resin composition constituting the prepreg layer may contain an epoxy resin and 1 to 100 parts by mass of the carbon-based powder per 100 parts by mass of the epoxy resin (solid content equivalent).

[6] The thermosetting resin composition constituting the resin layer may contain an epoxy resin and 100 to 2,000 parts by mass of the graphite per 100 parts by mass of the epoxy resin (solid content equivalent).

To achieve the above object, [7] the method for manufacturing a fuel cell separator member according to the present invention comprises the steps of: impregnating a substrate with a thermosetting resin composition containing carbon-based powder to produce a prepreg layer; forming a thermosetting resin composition containing flake-like graphite into a sheet to produce a resin layer; and laminating the resin layers on both sides of the prepreg layer and integrating the prepreg layer and the resin layer by applying pressure.

To achieve the above object, [8] the fuel cell separator of the present invention comprises a substrate and a matrix layer containing flaky graphite and a resin, the substrate is embedded in the matrix layer, the main surface of the graphite is parallel or inclined to the main surface of the matrix layer in the surface region of the matrix layer, and the inclination of the main surface of the graphite to the main surface of the matrix layer in the region near the substrate is greater than the inclination of the main surface of the graphite present in the surface region of the matrix layer.

[9] Furthermore, the density of the graphite in the surface region of the matrix layer is higher than the density of the graphite in the adjacent region of the substrate.

[10] It is also preferable that the resin is composed of a thermosetting resin composition.

[11] The substrate may also be made of a woven fabric.

The present invention can provide a fuel cell separator having low penetration resistivity and volume resistivity, a fuel cell separator member constituting the fuel cell separator, and a method for manufacturing the fuel cell separator member.

1 is a schematic cross-sectional view showing a structure of a fuel cell separator member according to an embodiment. FIG. 2 is an overall configuration diagram showing a process for producing a prepreg layer of the fuel cell separator member according to the embodiment. FIG. 2 is an overall configuration diagram showing a process for producing a resin layer of a fuel cell separator member according to an embodiment. 1A to 1C are schematic cross-sectional views illustrating a method for producing a fuel cell separator member according to an embodiment. 1 is a schematic plan view showing a configuration of a fuel cell separator according to an embodiment. 6 is a schematic cross-sectional view taken along line VV in FIG. 5. 3 is a schematic cross-sectional view showing a method for integrating fuel cell separators according to an embodiment. FIG.

The following provides a detailed explanation of a fuel cell separator member, a method for manufacturing a fuel cell separator member, and a fuel cell separator according to a form for carrying out the present invention (hereinafter simply referred to as "embodiment"). The embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out with appropriate modifications within the scope of its gist.

In the following description, identical or similar components are given the same reference numerals, and duplicated descriptions are omitted. Furthermore, as terms used in this invention, the B stage refers to a state in which the curing reaction of the resin composition has not progressed completely. The C stage refers to a state in which the curing reaction of the resin composition has progressed almost completely.

The following will be explained in the order of fuel cell separator member, manufacturing method of fuel cell separator member, fuel cell separator, and manufacturing method of fuel cell separator.

(Fuel cell separator member 10)
A fuel cell separator member 10 according to an embodiment will be described. As shown in FIG. 1, the fuel cell separator member 10 has a structure in which a resin layer 11 is laminated on both sides of a prepreg layer 13. The fuel cell separator member 10 is obtained by laminating the resin layer 11 on the prepreg layer 13, and heating the prepreg layer 13 and the resin layer 11 at a temperature at which the prepreg layer 13 and the resin layer 11 are in close contact with each other. The fuel cell separator member 10 is in a cured state of B stage. The fuel cell separator member 10 having such a structure can be used as a member of a fuel cell separator 60 constituting a fuel cell (a member before being processed into a fuel cell separator).

The prepreg layer 13 and the resin layer 11 will be explained.

(Prepreg layer 13)
The prepreg layer 13 is formed by impregnating a base material with a thermosetting resin composition containing carbon-based powder. The cured state of the prepreg layer 13 is in the B stage.

The thickness of the prepreg layer 13 depends on the thickness of the fuel cell separator itself, but is preferably 40 to 200 μm, and from the viewpoint of electrical conductivity, is more preferably 50 to 150 μm.

From the viewpoint of ensuring the electrical conductivity of the fuel cell separator, the volume resistivity of the prepreg layer 13 is preferably 500 mΩ·cm or less, and more preferably 400 mΩ·cm or less. Here, the cured state of the prepreg layer 13 used in measuring the volume resistivity is the C stage.

The substrate preferably has openings from the viewpoint of heating the fuel cell separator member 10 composed of the resin layer 11 and the prepreg layer 13 and flowing the resin components of the molten resin layer 11 and the prepreg layer 13. An example of a substrate having openings is a woven fabric.

A woven fabric is a fabric made by weaving warp and weft threads. The weave is not particularly limited, but examples include plain weave, twill weave, and satin weave.

The woven fabric has gaps between the warp and weft threads, i.e., openings, which are formed when the weft threads are woven into the warp threads. The size of the openings is preferably 0.01 to 0.20 ^mm2 from the viewpoint of reducing the penetration resistivity of the fuel cell separator 60 after the fuel cell separator member 10 is molded. Furthermore, the presence of these openings improves the fluidity of the resin when the resin component of the fuel cell separator member 10 melts during the process of producing the fuel cell separator 60 (particularly the process of heating and pressing), which will be described later.

The intersections of the warp and weft threads (intersections of the warp and weft threads) are preferably fused, welded or glued in order to facilitate the formation of conductive paths resulting from the carbon powder. One example of a woven fabric in which the intersections of the warp and weft threads are fused is polyester mesh.

The material of the substrate is not particularly limited, but examples include resin-based materials, glass-based materials, and carbon-based materials.

Examples of resin-based materials include thermosetting resins such as polyimide, and thermoplastic resins such as polyamide, polyamideimide, polyphenylene sulfide, polyethersulfone, polyethylene, polypropylene, polyethylene terephthalate, and polyethylene naphthalate.

Examples of glass-based materials include T-glass, E-glass, C-glass, S-glass, and D-glass. From the viewpoint of availability, E-glass is preferred.

Examples of carbon-based materials include PAN (polyacrylonitrile)-based carbon and pitch-based carbon.

The thickness of the substrate is preferably 40 to 200 μm in order to obtain a prepreg layer 13 that is light and thin and has high strength.

From the viewpoint of improving the adhesion between the substrate and the thermosetting resin composition, it is preferable that the surface of the substrate is subjected to a silane coupling treatment, a plasma treatment, or a roughening treatment.

The thermosetting resin composition constituting the prepreg layer 13 is not particularly limited, but is preferably an epoxy-based resin composition with epoxy resin as the main component.

The epoxy resin is not particularly limited, but at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, amine type epoxy resin, biphenyl type epoxy resin, and alicyclic epoxy resin can be used. From the viewpoints of processability and heat resistance, novolac type epoxy resin is preferable.

The material constituting the carbon-based powder is not particularly limited, but examples include carbon black, graphite, carbon chop, etc. From the viewpoints of electrical conductivity and processability, carbon black is preferred. Two or more types of carbon-based powders can be used in combination.

The carbon black is not particularly limited, but examples include furnace black, channel black, thermal black, and acetylene black. Two or more types of carbon black may be mixed. From the viewpoint of improving electrical conductivity, acetylene black is preferred.

The amount of carbon-based powder is 1 to 100 parts by mass per 100 parts by mass of epoxy resin (solid content equivalent). From the viewpoint of processability, it is more preferably 5 to 50 parts by mass.

(Resin layer 11)
The resin layer 11 is made of a thermosetting resin composition containing graphite, and is in a cured state of the B stage.

The thickness of the resin layer 11 depends on the thickness of the fuel cell separator itself, but is preferably 50 to 400 μm, and from the viewpoint of maintaining lightness and strength, is 100 to 300 μm.

From the viewpoint of ensuring the electrical conductivity of the fuel cell separator, the volume resistivity of the resin layer 11 is preferably 20 mΩ·cm or less, and more preferably 15 mΩ·cm or less. Here, the cured state of the resin layer 11 used in measuring the volume resistivity is the C stage.

The thermosetting resin composition constituting the resin layer 11 is not particularly limited, but examples thereof include an epoxy resin composition mainly made of an epoxy resin, a phenolic resin composition mainly made of a phenolic resin, a polyimide resin composition mainly made of a thermosetting polyimide resin, a melamine resin composition mainly made of a melamine resin, a urethane resin composition mainly made of a urethane resin, a diallyl phthalate resin composition mainly made of a diallyl phthalate resin, an unsaturated polyester resin composition mainly made of an unsaturated polyester resin, and a cyanate ester resin composition mainly made of a cyanate ester resin. From the viewpoints of heat resistance, durability, and processability, an epoxy resin composition is preferable.

The epoxy resin used as the base resin in the epoxy resin composition is not particularly limited, but at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, amine type epoxy resin, biphenyl type epoxy resin, and alicyclic epoxy resin can be used. From the viewpoints of processability and heat resistance, novolac type epoxy resin is preferable.

Examples of graphite include artificial graphite and natural graphite. From the viewpoint of cost, natural graphite is preferred. Among natural graphite, from the viewpoint of electrical conductivity, expanded graphite, flake graphite, or exfoliated graphite is preferred. Two or more types can be used in combination.

The shape of the graphite is preferably a flake shape having a main surface from the viewpoint of improving the electrical conductivity of the fuel cell separator, i.e., from the viewpoint of reducing the through-hole resistivity and volume resistivity. Examples of flake shapes having a main surface include a leaf shape, a scale shape, etc.

The size of the graphite is 1 to 100 μm from the viewpoint of expressing the electrical conductivity of the resin layer 11 and maintaining the shape and strength of the resin layer 11 when the resin layer 11 is processed into a sheet. The size of the graphite refers to the distance between two ends on the main surface of the graphite, and is the greatest distance between the ends.

From the viewpoints of electrical conductivity and processability, the amount of graphite is 100 to 2,000 parts by mass per 100 parts by mass of epoxy resin (solid content equivalent). From the viewpoints of gas leakage and electrical conductivity of the fuel cell separator, the amount of graphite is more preferably 150 to 400 parts by mass.

The resin layer 11 contains voids. The voids exist between the graphite particles contained in the thermosetting resin composition that constitutes the resin layer 11. The presence of these voids promotes the flow of the resin. That is, when the resin layer 11 is heated, the resin of the thermosetting resin composition that constitutes the resin layer 11 melts, and the molten resin enters the voids, promoting the flow of the resin. As a result, the graphite is also arranged in such a way that the penetration resistivity and volume resistivity of the fuel cell separator are low.

The volume resistivity of the resin layer 11 is lower than that of the prepreg layer 13. As a result, by processing the fuel cell separator member 10 into a fuel cell separator, the penetration resistivity and volume resistivity of the fuel cell separator 60 are reduced. The cured state of the resin layer 11 and prepreg layer 13 used in measuring the volume resistivity is the C stage.

Another layer may be laminated between the resin layer 11 and the prepreg layer 13, and may be a single layer or multiple layers. For example, when the other layer is a single layer, the other layer is composed of, for example, a thermoplastic resin composition or the above-mentioned thermosetting resin composition. The presence of the other layer improves the gas barrier properties of the fuel cell separator.

When the other layers are composed of a thermoplastic resin composition, examples of the thermoplastic resin composition include an acrylic resin composition based on an acrylic resin, a polyimide resin composition based on a thermoplastic polyimide resin, a polyamide resin composition based on a polyamide resin, a polyethersulfone resin composition based on a polyethersulfone resin, a phenoxy resin composition based on a phenoxy resin, a polypropylene resin composition based on a polypropylene resin, a polycarbonate resin composition based on a polycarbonate resin, a polyethylene resin composition based on a polyethylene resin, a polyester resin composition based on a polyester resin, an acrylonitrile butadiene styrene resin composition based on an acrylonitrile butadiene styrene (ABS) resin, a polystyrene resin composition based on a polystyrene (PS) resin, a polyphenylene sulfide resin composition based on a polyphenylene sulfide (PPS) resin composition, and a polyamideimide resin composition based on a polyamideimide (PAI) resin.

From the viewpoints of heat resistance, durability, adhesion, and processability, polyethersulfone-based resin compositions and polypropylene-based resin compositions are preferred, and from the viewpoint of gas barrier properties, polyethersulfone-based resin compositions are preferred. Two or more types of resin compositions may be mixed and used.

Next, a method for manufacturing the fuel cell separator member 10 according to the embodiment will be described.

(Method of manufacturing fuel cell separator member 10)
The manufacturing method of the fuel cell separator member 10 of the embodiment includes the steps of impregnating a substrate with a thermosetting resin composition containing carbon-based powder to produce a prepreg layer 13, forming the thermosetting resin composition containing flaky graphite into a sheet to produce a resin layer 11, and laminating resin layers 11 on both sides of the prepreg layer 13 and integrating the prepreg layer 13 and the resin layer 11 by applying pressure.

First, we will explain the method of producing the prepreg layer 13 by impregnating a substrate with a thermosetting resin composition containing carbon-based powder.

(Method for manufacturing prepreg layer 13)
Fig. 2 shows an apparatus for producing the prepreg layer 13. In Fig. 2, upstream and downstream refer to the upstream and downstream in the conveying direction, and up and down refer to the top and bottom directions in the production line 20 for the prepreg layer 13.

The feed roll 110 has the substrate 90 wound around its outer circumference before processing. The feed roll 110 supplies the substrate 90 downstream. The substrate 90 is transported via guide rolls 101 and 102 to a resin impregnation section 120 filled with resin 121 made of a thermosetting resin composition containing carbon-based powder. The substrate 90 is impregnated with the resin 121 in the resin impregnation section 120, and is transported via guide roll 103 to a resin drying section 130 where the resin 121 is dried.

After passing through the resin drying section 130, the upper and lower surfaces of the substrate 90 are covered with the separation film 160 and the separation film 150 supplied from the separation film supply section 106 and the separation film supply section 107. The substrate 90 is pressed by the lamination roll 104 and the lamination roll 105 with the upper and lower surfaces covered with the separation film 160 and the separation film 150.

The pressed substrate 90 is wound up by a winding roll 140. The wound substrate 90 is a prepreg layer 13 in which the substrate 90 is impregnated with a thermosetting resin composition containing carbon-based powder.

The substrate 90 after passing through the resin drying section 130 corresponds to the prepreg layer 13 in FIG. 1.

The delivery roll 110 is disposed at the most upstream side of the transport path. The delivery roll 110 is supported so as to be rotatable. This allows the delivery roll 110 to deliver the substrate 90. The delivery roll 110 can be rotated by a drive mechanism such as a motor. It may also be a mechanism capable of being driven by the rotation of the take-up roll 140.

The resin impregnation section 120 is located downstream of the delivery roll 110. The container of the resin impregnation section 120 is filled with resin 121, which is a thermosetting resin composition containing carbon-based powder whose viscosity is adjusted to be suitable for application.

An impregnation roll 122 is installed in the resin impregnation section 120. The impregnation roll 122 is installed so that at least a portion of the impregnation roll 122 is immersed in the resin 121. The substrate 90 transported by the guide roll 102 passes through the resin 121 along the outer periphery of the impregnation roll 122.

At this time, the base material 90 is impregnated with the resin 121. The amount of resin 121 impregnated is adjusted by the viscosity of the resin 121 and the speed at which the base material 90 is transported. This makes it possible to adjust the thickness of the prepreg layer 13, i.e., the amount of resin 121 impregnated into the base material 90.

The resin drying section 130 is disposed downstream of the resin impregnation section 120. The resin drying section 130 dries the resin 121 impregnated into the substrate 90 by blowing air. Drying may be performed by blowing air while heating. The drying conditions are appropriately adjusted depending on the amount of resin 121 impregnated into the substrate 90, the cured state of the resin 121 after passing through the resin drying section 130, the length of the resin drying section 130, and the conveying speed.

After passing through the resin drying section 130, the cured state of the resin 121 impregnated into the substrate 90 is in the B stage.

The separate film supply unit 106, the separate film supply unit 107, the laminating roll 104, and the laminating roll 105 are arranged between the resin drying unit 130 and the winding roll 140.

The separate film supply unit 106 supplies the separate film 160 to the upper surface of the substrate 90. The separate film supply unit 107 supplies the separate film 150 to the lower surface of the substrate 90.

The laminating rolls 104 and 105 apply pressure to the separate films 150 and 160 supplied to the upper and lower surfaces of the substrate 90 while bonding them together.

A heating device may be attached to the laminating rolls 104 and 105, and the separating film 150 and the separating film 160 may be bonded to the laminating rolls 104 and 105 in a heated state.

It is preferable that the separate film 150 and the separate film 160 are subjected to a release treatment at least on the surface that contacts the substrate 90.

Separate film 150 and separate film 160 may be subjected to different release treatments to give them different peel strengths. By utilizing this difference in peel strength, the separate film attached to substrate 90 can be easily peeled off. Also, the separate film can be peeled off only from one side of substrate 90.

Although this depends on the surface condition of the resin 121 after drying, if the surface of the substrate 90 that has passed through the resin drying section 130 is not sticky (tacky), it is not necessary to use a separate film. This can simplify the production line 20.

The winding roll 140 is installed at the most downstream side of the transport path. The winding roll 140 is supported in a rotatable state. The winding roll 140 winds up the laminate 170, which is made up of the separate film 160, the base material 90 (prepreg layer 13), and the separate film 150 stacked in this order from the top.

Next, we will explain the method of producing the resin layer 11 by forming a thermosetting resin composition containing flaky graphite into a sheet.

(Method for manufacturing resin layer 11)
3 shows an apparatus for producing the resin layer 11. In FIG. 3, upstream and downstream refer to the upstream and downstream in the conveying direction, and top and bottom refer to the top and bottom directions in a production line 30 for the resin layer 11.

The delivery roll 111 has a separate film 151 wound around its outer circumference. The delivery roll 111 supplies the separate film 151. The separate film 151 passes under a resin coating section 210 that coats the resin layer resin 220, which is made of a thermosetting resin composition containing graphite. In the resin coating section 210, the separate film 151 is coated with the resin layer resin 220 on its upper surface, and is then transported to a resin drying section 131 that dries the resin layer resin 220.

The separate film 151 that has passed through the resin drying section 131 is taken up by the take-up roll 141. The taken-up separate film 151 has a sheet-shaped resin for the resin layer 220 formed on the upper surface of the separate film 151.

The delivery roll 111 is disposed at the most upstream side of the transport path. The delivery roll 111 is supported so as to be rotatable. This allows the delivery roll 111 to deliver the separation film 151. The delivery roll 111 can be rotated by a drive mechanism such as a motor. It may also be a mechanism that can follow the rotation of the take-up roll 141. A release treatment is applied to the surface (upper surface) of the separation film 151 delivered from the delivery roll 111 on which the resin layer resin 220 is applied.

The resin coating unit 210 is disposed downstream of the delivery roll 111. The resin coating unit 210 coats the upper surface of the separation film 151 that has been subjected to a release treatment with a resin 220 for the resin layer. The resin coating unit 210 is not particularly limited, but examples thereof include known coaters. Examples include a die coater, a comma coater, and a gravure coater. The amount of resin 220 for the resin layer supplied from the resin coating unit 210 is adjusted according to the viscosity of the resin 220 for the resin layer, the conveying speed, etc., so that the thickness of the resin layer 11 after drying is 100 to 300 μm.

The resin drying section 131 is disposed downstream of the resin application section 210. The resin drying section 131 dries the resin for resin layer 220 applied to the separation film 151 by blowing air. Drying may be performed by blowing air while heating. The drying conditions are appropriately adjusted depending on the amount of resin for resin layer 220 applied, the cured state of the resin for resin layer 220 after passing through the resin drying section 131, the length of the resin drying section 131, and the conveying speed.

The cured state of the resin 220 for the resin layer that has passed through the resin drying section 131 is B stage. After passing through the resin drying section 131, the resin 220 for the resin layer that has been formed into a sheet shape (not shown) corresponds to the resin layer 11 in FIG. 1.

The winding roll 141 is installed at the most downstream side of the transport path. The winding roll 141 winds up a laminate (not shown) in which the resin for the resin layer 220 (resin layer 11) formed in a sheet shape and the separation film 151 are laminated in this order from the top.

If the surface of the resin for resin layer 220 after drying is sticky (tacky), the underside of the separate film 151 may also be subjected to a release treatment. That is, both sides of the separate film 151 may be subjected to a release treatment. This makes it possible to prevent adhesion between the underside of the separate film 151 and the resin for resin layer 220 (resin layer 11) even when the laminate in which the resin for resin layer 220 (resin layer 11) and the separate film 151 are laminated in this order is wound up on the winding roll 141.

As an alternative method, the separate film supply unit and laminating roll may be placed between the resin drying unit 131 and the winding roll 141. This allows the exposed surface of the resin for the resin layer 220 to be covered with the separate film, so that even when wound up by the winding roll 141, the resin for the resin layer 220 does not stick to the underside of the separate film 151.

Next, we will explain the method of laminating resin layers 11 on both sides of the prepreg layer 13 and integrating the prepreg layer 13 and the resin layer 11 by applying pressure.

(Integration of prepreg layer 13 and resin layer 11)
FIG. 4 shows an apparatus for laminating resin layers 11 on both sides of a prepreg layer 13 and integrating them together.

First, the prepreg layer 13 (laminate 170) is cut to a predetermined size. The separate film 150 and the separate film 160 are peeled off from the laminate 170 to obtain the prepreg layer 13.

Next, the sheet-like resin 220 for the resin layer formed on the upper surface of the separate film 151, i.e., the resin layer 11 formed on the upper surface of the separate film 151, is cut to the same size as the prepreg layer 13. After cutting, the separate film 151 is peeled off to obtain the resin layer 11.

Next, the obtained prepreg layer 13 and resin layer 11 are integrated. Resin layers 11 are laminated on both sides of the prepreg layer 13. After lamination, pressure is applied in the direction of the arrow using a press 300, and heating is performed to integrate the prepreg layer 13 and the resin layer 11 so that they are in close contact with each other. The integrated laminate is the fuel cell separator member 10. The cured state of the fuel cell separator member 10 is in the B stage.

When integrating, the separate film 151 may be integrated without being peeled off from the resin layer 11 (sheet-shaped resin 220 for the resin layer).

The conditions for heating and pressing can be appropriately selected depending on the thickness of the fuel cell separator member 10, but are 20 to 350°C, 0.1 to 50 MPa, and 5 to 300 seconds. The cured state of the prepreg layer 13 and resin layer 11 of this laminate (fuel cell separator member 10) is in the B stage.

In the above-mentioned method for producing the prepreg layer 13 and the resin layer 11, an organic solvent can be added to the resin composition constituting the prepreg layer 13 and the resin layer 11. This allows the viscosity of the resin composition to be adjusted, and the prepreg layer 13 and the resin layer 11 can be produced.

Examples of organic solvents that can be used include alcohols such as methanol and ethanol; glycols such as ethylene glycol and propylene glycol; glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; glycol dialkyl ethers such as ethylene glycol dimethyl ether and ethylene glycol diethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbons such as hexane, cyclohexane, and octane; amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; cyclic ethers such as tetrahydrofuran and dioxane, methyl acetate, ethyl acetate, and propyl acetate.

(Another method for manufacturing the fuel cell separator member 10)
The fuel cell separator member 10 can also be made by other methods.

First, prepare the resin layer 11 and a resin sheet made of a thermosetting resin composition containing carbon-based powder. The resin sheet made of a thermosetting resin composition containing carbon-based powder is produced in the same manner as the resin layer 11 is produced by forming a thermosetting resin composition containing flaky graphite into a sheet.

These are layered on both sides of the substrate 90 in the order of closest to the substrate 90, the resin sheet, and the resin layer 11, with the substrate 90 before being impregnated with resin at the center. After layering, these are heated and pressurized to be integrated, and the fuel cell separator member 10 is obtained.

The fuel cell separator member 10 can also be produced by other methods.

First, prepare the resin layer 11 and a resin sheet made of a thermosetting resin composition containing carbon-based powder. The resin sheet made of a thermosetting resin composition containing carbon-based powder is produced in the same manner as the resin layer 11 is produced by forming a thermosetting resin composition containing flaky graphite into a sheet.

These are laminated on both sides of the base material 90, with the base material 90 before being impregnated with resin at the center. After lamination, these are heated and pressurized to obtain the prepreg layer 13.

Next, the resin layer 11 and the prepreg layer 13 are laminated in the following order: resin layer 11, prepreg layer 13, resin layer 11. After lamination, the layers are heated and pressurized. This causes the resin layer 11 and the prepreg layer 13 to adhere to each other, and the fuel cell separator member 10 is obtained.

The fuel cell separator member 10 can also be produced by other methods.

First, prepare the resin layer 11 and a resin sheet made of a thermosetting resin composition containing carbon-based powder. The resin sheet made of a thermosetting resin composition containing carbon-based powder is produced in the same manner as the resin layer 11 is produced by forming a thermosetting resin composition containing flaky graphite into a sheet.

These are layered in the following order:

First, a resin sheet is laminated on one side of the substrate 90 before it is impregnated with resin. After lamination, the substrate is heated and pressurized to obtain the prepreg layer 13.

Next, resin layers 11 are laminated on both sides of the prepreg layer 13. After lamination, the layers are heated and pressurized. This bonds the resin layer 11 and the prepreg layer 13 together, resulting in the fuel cell separator member 10.

At this time, it is preferable that the thickness of the resin sheet is at least twice the thickness of the substrate 90 in order to uniformly impregnate the substrate 90 with the resin.

Next, the fuel cell separator 60 according to the embodiment will be described. Note that any explanation that overlaps with the explanation of the fuel cell separator member 10 will be omitted.

(Fuel cell separator 60)
The fuel cell separator 60 of the embodiment is obtained by heating and pressurizing the fuel cell separator member 10 (cured in a B stage) in which the resin layer 11 is laminated and bonded on both sides of the prepreg layer 13. In addition, the resin component constituting the prepreg layer 13 and the resin component constituting the resin layer 11 melt by this heating and pressurization, and the prepreg layer 13 and the resin layer 11 are integrated. The fuel cell separator 60 in which the resin component constituting the prepreg layer 13 and the resin component constituting the resin layer 11 are integrated includes a substrate 90 and a matrix layer 500 containing flaky graphite 62 and a resin, and the substrate 90 is embedded in the matrix layer 500. The substrate 90 is a substrate constituting the prepreg layer 13. The matrix layer 500 is a thermosetting resin composition containing the carbon-based powder constituting the prepreg layer 13 and a thermosetting resin composition containing graphite constituting the resin layer 11. In the following description, a woven fabric is used as the substrate 90.

As shown in FIG. 5, the substrate 90 shown by the dashed line is embedded in the matrix layer 500. The surface of the fuel cell separator 60 is formed by the matrix layer 500.

Figure 6 is a V-V cross-sectional view of the fuel cell separator 60 shown in Figure 5. As shown in Figure 6, the fuel cell separator 60 includes a substrate 90 and a matrix layer 500, and the substrate 90 is embedded in the matrix layer 500.

The hardened state of the fuel cell separator 60 is in C stage.

The fuel cell separator 60 having such a configuration has low penetration resistance and volume resistivity, and is suitable for use as a fuel cell separator that constitutes a fuel cell.

The state of the graphite 62 present in the matrix layer 500 is explained below.

As shown in an enlarged view in circle 1 of FIG. 6, there are a number of flake-shaped graphite 62 in the vicinity of the substrate 90 embedded in the matrix layer 500. Most of these graphite 62 are present with the main surface of the graphite 62 inclined relative to the main surface of the matrix layer 500. This inclination is greater than the inclination of the graphite 62 present in the surface region of the matrix layer 500. Here, the surface region of the matrix layer 500 refers to the region from the main surface of the matrix layer 500 to a depth equivalent to 10% of the thickness of the matrix layer 500. The region adjacent to the substrate 90 refers to the region from the surface of the substrate 90 to a depth equivalent to 10% of the thickness of the matrix layer 500. The inclination of the graphite 62 is the average inclination of the inclination of the multiple graphite 62 that could be observed when the cross section of the matrix layer 500 was observed using a scanning electron microscope.

The inventors speculate that the reason why the penetration resistance and volume resistivity of the fuel cell separator 60 having such a configuration are low is as follows.

As shown enlarged in circle 1 in Figure 6, the graphite 62 with a large inclination is present in large amounts in the region adjacent to the substrate 90. Furthermore, carbon-based powder (not shown) is present in the matrix layer 500. This carbon-based powder is also present between the multiple graphite particles 62 that are present in large amounts in the region adjacent to the substrate 90, making it easier to form conductive circuits. In other words, conductive paths are more likely to be formed in the thickness direction of the fuel cell separator 60. As a result, the penetration resistivity of the fuel cell separator 60 is lower.

As shown enlarged in circle 2 in FIG. 6, flake-shaped graphite 62 is also present in the surface region of the matrix layer 500. The graphite 62 is present in greater amounts in the surface region of the matrix layer 500 than in the region adjacent to the substrate 90, and is present at a higher density. This improves the electrical conductivity of the fuel cell separator 60. Furthermore, the main surface of the graphite 62 in the surface region of the matrix layer 500 is present parallel to or inclined relative to the main surface of the matrix layer 500. This makes it easier for conductive paths to be formed in the direction of the main surface of the matrix layer 500, and reduces the volume resistivity of the fuel cell separator 60.

This type of structure is formed when the fuel cell separator member 10 is heated and pressurized to melt and flow the resin components constituting the prepreg layer 13 and the resin components constituting the resin layer 11, and the molten resin components move into the voids contained in the resin layer 11 that constitutes the fuel cell separator member 10.

In addition, due to the flow of the resin component, in the surface region of the matrix layer 500, the main surface of the graphite 62 tends to be arranged at a tilt that is parallel or close to parallel to the main surface of the matrix layer 500. In addition, in the region near the substrate 90, particularly near the opening of the substrate 90, the flow of the resin becomes large, so that the main surface of the graphite 62 tends to be arranged at a large tilt to the main surface of the surface of the matrix layer 500. The substrate 90 having the opening is embedded in the matrix layer 500, and the matrix layer 500 is also present in the opening. Although the matrix layer 500 is present in the opening, the term "opening" will be used as it is for the purpose of explanation.

The main surface refers to the surface of the fuel cell separator 60 (the surface of the matrix layer 500) that is parallel to the horizontal direction when the fuel cell separator 60 is placed on a horizontal stand.

Next, we will explain the manufacturing method of the fuel cell separator 60.

(Method of manufacturing fuel cell separator 60)
7, fuel cell separator 60 is obtained by inserting fuel cell separator member 10 in a B-stage state between dies 400, and applying pressure in the direction of the arrow using a press 310 and heating. The hardened state of fuel cell separator 60 obtained at this time is in a C-stage.

The surface shape of the fuel cell separator 60 is formed by a mold 400.

The heating and pressurizing conditions are set appropriately depending on the thickness of the fuel cell separator member 10. For example, 100 to 200°C, 5 to 30 MPa, and 5 to 120 seconds.

The mold 400 is, for example, a mold in which grooves with uneven shapes are formed. These grooves become the flow paths for gases, etc. in the fuel cell.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

The following materials were used in the examples and comparative examples.

(1) Base resin: cresol novolac type epoxy resin, epoxy equivalent 211 g/eq (manufactured by Nippon Kayaku Co., Ltd., EOCN-102S-70);
(2) Hardener: Novolac type phenolic resin, hydroxyl equivalent 105 g/eq (manufactured by AICA Corporation, BRG-556);
(3) Reinforcing agent: phenoxy resin (YP-50, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.),
(4) Curing accelerator: 2-undecylimidazole (manufactured by Shikoku Chemical Industries, Ltd., C11Z),
(5) Conductive filler A: exfoliated graphite, average particle size 5 μm (manufactured by Denka Company, 100% Denka Black Press),
(6) Conductive filler B: exfoliated graphite, average particle size 15 μm (manufactured by Denka Company, Denka Black 100% Press),
(7) Conductive filler C: spherical graphite, average particle size 35 μm (manufactured by Denka Company, Denka Black 100% pressed),
(8) Conductive filler D: acetylene black (manufactured by Denka Company, 100% pressed Denka Black).

In the examples and comparative examples, the following substrates were used.
(1) Polyester mesh (manufactured by Nippon Tokushu Orimono Co., Ltd., TNo. 60SS).

In the examples and comparative examples, the samples were prepared, measured, and evaluated as follows.

The preparation, measurement, and evaluation methods of the prepreg layer, resin layer, and fuel cell separator member are explained using Example 1 as an example.

(1) (Preparation of prepreg layer)
(1-1) (Resin composition for prepreg layer)
100.0 parts by mass of the base agent, 48.8 parts by mass of the curing agent, and 17.5 parts by mass of the reinforcing agent were dissolved in methyl ethyl ketone, and then added to one container and mixed to prepare a mixed solution. Next, a solution in which 3.0 parts by mass of the curing accelerator was dissolved in methanol, and 43.8 parts by mass of the conductive filler D were added to the mixed solution. After addition, the mixture was stirred with a homomixer to obtain a solution of a resin composition for a prepreg layer. The stirring conditions were room temperature, 6000 rpm, and 30 minutes. In addition, methyl ethyl ketone was added so that the viscosity of the solution was within the range of 100 to 3000 mPa·s, and a resin composition for a prepreg layer was obtained.

(1-2) Preparation of Prepreg Layer The resin composition for the prepreg layer was applied to the release surface of a 38 μm-thick release-treated film (PET38X, manufactured by Lintec Corporation) using a bar coater so that the thickness after drying would be 20 μm, and then dried. The drying conditions were 70° C. and 4 minutes. After cooling, a resin sheet for the prepreg layer having a thickness of 20 μm was obtained.

Next, the resin surface of the prepreg layer resin sheet was overlapped with a polyester mesh, and the pieces were bonded together using a laminator (TAISEI LAMINATOR CO., LTD., VA-700) at 80°C, 0.4 m/min, and 0.6 MPa. After cooling, the release-treated film was peeled off to obtain a prepreg layer.

(2) (Preparation of resin layer)
(2-1) Resin layer resin composition 100.0 parts by mass of the main agent, 48.4 parts by mass of the curing agent and 35.0 parts by mass of the reinforcing agent were dissolved in methyl ethyl ketone, and then mixed together in one container to prepare a mixed solution. Next, a solution in which 3.0 parts by mass of the curing accelerator was dissolved in methanol and 559.0 parts by mass of the conductive filler A were added to the mixed solution, and the mixture was stirred at room temperature to obtain a solution of the resin layer resin composition. In addition, methyl ethyl ketone was added so that the viscosity of the solution was within the range of 100 to 3000 mPa·s, and a resin layer resin composition was obtained.

(2-2) Preparation of Resin Sheet for Resin Layer The resin composition for the resin layer was applied to the release surface of a 38 μm-thick release-treated film (PET38X, manufactured by Lintec Corporation) with a bar coater so that the thickness after drying would be 250 μm, and then dried. The drying conditions were 70° C. and 7 minutes. After cooling, a resin sheet for the resin layer having a thickness of 250 μm was obtained.

(3) (Fabrication of Fuel Cell Separator Member)
The resin layer resin sheets were laminated on the front and back surfaces of the prepreg layer so that the resin surfaces of the resin layer resin sheets faced each other. Then, the prepreg layers were laminated under conditions of 80° C., 0.4 m/min, and 0.6 MPa. After cooling, the release-treated film of the resin layer sheet was peeled off to obtain a fuel cell separator member.

As samples to be used for various measurements, characteristic evaluation samples for evaluating the characteristics of a fuel cell separator, a prepreg layer alone, and a resin layer alone were prepared.
(4) (Preparation of sample for characteristic evaluation)
The characteristic evaluation samples were cut out from the fuel cell separator member, the prepreg layer alone, and the resin layer alone in a square shape of 100 mm x 100 mm. Next, a release-treated film (PET3811 manufactured by Lintec Corporation) having a thickness of 38 μm was laminated on both sides of each cut-out sample so that the release-treated surface was aligned. Press molding was performed under conditions of 180° C., 5 minutes, and 20 MPa so that the cured state of each laminated sample was C stage. After cooling, characteristic evaluation samples of the fuel cell separator, the prepreg layer alone, and the resin layer alone were obtained.

Here, the sample for evaluating the characteristics of the fuel cell separator was designated as characteristic evaluation sample 1, the sample for evaluating the characteristics of the prepreg layer alone was designated as characteristic evaluation sample 2, and the sample for evaluating the characteristics of the resin layer alone was designated as characteristic evaluation sample 3.

<Measurement of Volume Resistivity>
The volume resistivity (mΩ·cm) of the characteristic evaluation sample 1 was measured by a four-probe method in accordance with JIS K7194 using a resistivity meter (RM3545, manufactured by Hioki E.E. Corporation). The volume resistivities of the characteristic evaluation samples 2 and 3 were also measured in the same manner.

<Measurement of penetration resistance>
A sample for measuring the penetration resistivity was prepared as follows. First, two sheets of the characteristic evaluation sample 1 prepared in (4) were stacked. After stacking, a gas diffusion layer substrate (GDL MFL, manufactured by Mitsubishi Chemical Corporation) was laminated on each of the two outer surfaces to obtain a measurement sample.

The penetration resistance was measured by contacting gold-plated electrodes to the two outer surfaces of the measurement sample (the two surfaces on which the gas diffusion layer was exposed) and passing a current under a pressure of 1 MPa.

<Measurement of bending strength>
(1) Preparation of Measurement Sample The characteristic evaluation sample 1 was cut into a rectangle having a width of 10 mm and a length of 20 mm, which was used as a measurement sample.
(2) Measurement method The bending strength was measured using an autograph testing machine (AG-10, manufactured by Shimadzu Corporation). The measurement was performed by three-point bending (support distance 10 mm, test speed 2 mm/min) to measure the breaking load. The bending strength was calculated from the obtained maximum bending stress (maximum bending stress that the test piece can withstand) in accordance with JIS K7171.

<Gas barrier properties>
The gas barrier property was evaluated by measuring the water vapor permeability.
(1) Preparation of Measurement Samples The characteristic evaluation sample 1 was cut into a circular shape with a diameter of 76 mm to prepare a measurement sample.
(2) Measurement method The water vapor permeability was determined in accordance with JIS Z 0208. Specifically, the amount of water vapor that permeated the measurement sample in 24 hours under conditions of 40°C and 90% RH was calculated as a value per square ^meter (g/ ^m2 ·24h).

The evaluation criteria were as follows:
Excellent: Water vapor transmission rate is less than 13 g/ ^m2 ·24 h.
Good: Water vapor permeability is 13 g/ ^m2 ·24 h or more and less than 32 g/ ^m2 ·24 h.
Poor: Water vapor permeability is 32 g/ ^m2 ·24 h or more.

Examples 2 to 5 were prepared in the same manner as Example 1 described above, except that the type and content of each component was changed as shown in Table 1. In addition, for evaluation, samples for characteristic evaluation were prepared and evaluated in the same manner as Example 1.

The resin layer and fuel cell separator member of Comparative Example 1 are described below.

(Preparation of resin layer and resin sheet for resin layer)
The resin layer was prepared in the same manner as in Example 1.

(Preparation of fuel cell separator member)
The resin layer resin sheets were laminated on the front and back surfaces of the polyester mesh so that the resin surfaces of the resin layer resin sheets faced each other. Then, the sheets were laminated under conditions of 80° C., 0.4 m/min, and 0.6 MPa. After cooling, the release-treated film of the resin layer sheet was peeled off to obtain a fuel cell separator member.

Comparative Examples 2 to 3 were prepared in the same manner as Comparative Example 1 described above, except that the types and contents of each component were changed as shown in Table 1.

(Evaluation of fuel cell separator members and resin layer alone)
For the evaluation of Comparative Examples 1 to 3, a sample for evaluating the characteristics of a fuel cell separator (Sample for Evaluation of Characteristics 1) and a sample for evaluating the characteristics of the resin layer alone (Sample for Evaluation of Characteristics 3) were prepared in the same manner as in Example 1 and evaluated.

From the results in Table 1, the fuel cell separators of Examples 1 to 5 had good through-hole resistivity and volume resistivity. Furthermore, the fuel cell separators of Examples 1 to 5 had good gas barrier properties and bending strength while having low through-hole resistivity and volume resistivity. In this way, the present invention makes it possible to provide a fuel cell separator that is electrically conductive and has low through-hole resistivity and volume resistivity, a fuel cell separator member that constitutes a fuel cell separator, and a method for manufacturing a fuel cell separator member.

The fuel cell separator member, the manufacturing method for the fuel cell separator member, and the fuel cell separator of the present invention have industrial applicability.

10 Fuel cell separator member,
11 resin layer,
13 Prepreg layer,
20, 30 production lines,
60 Fuel cell separator,
62 graphite,
90 Substrate,
101, 102, 103 Guide roll,
104, 105 Laminate roll,
106, 107 Separate film supply unit,
110, 111: Sending roll,
120 resin impregnated portion,
121 resin,
122 Impregnation roll,
130, 131 resin drying section,
140, 141 Winding roll,
150, 151, 160 Separate film,
170 laminate,
210 resin coating part,
220 resin for resin layer,
300, 310 Press machine,
400 molds,
500 matrix layer.

Claims (8)

a prepreg layer in which a base material having an opening is impregnated with a thermosetting resin composition containing a carbon-based powder;
and a resin layer composed of a thermosetting resin composition containing graphite laminated on each of both sides of the prepreg layer,
The material of the substrate is polyethylene terephthalate or polyethylene naphthalate,
A fuel cell separator member, wherein the resin layer has a volume resistivity lower than a volume resistivity of the prepreg layer. The fuel cell separator member according to claim 1, wherein the substrate is made of a woven fabric. The fuel cell separator member according to claim 1 or 2, wherein the graphite has a flaky shape. The fuel cell separator member according to any one of claims 1 to 3, wherein the resin layer includes voids. 5. The fuel cell separator member according to claim 1, wherein the carbon-based powder is made of carbon black. 6. The fuel cell separator member according to claim 1, wherein the thermosetting resin composition constituting the prepreg layer comprises an epoxy resin, and 1 to 100 parts by mass of the carbon-based powder per 100 parts by mass (converted into solid content) of the epoxy resin. 7. The fuel cell separator member according to claim 1, wherein the thermosetting resin composition constituting the resin layer comprises an epoxy resin and 100 to 2000 parts by mass of the graphite per 100 parts by mass of the epoxy resin (converted into solid content). A step of impregnating a substrate made of polyethylene terephthalate or polyethylene naphthalate and having an opening with a thermosetting resin composition containing carbon-based powder to prepare a prepreg layer;
A step of forming a resin layer by forming a thermosetting resin composition containing flaky graphite into a sheet shape;
a step of laminating the resin layers on both sides of the prepreg layer and applying pressure to integrate the prepreg layer and the resin layer;
A method for manufacturing a fuel cell separator member comprising the steps of: